Development and evaluation of modified ZnCr-Shell particulates composite coatings: corrosion, structural, and microhardness properties

Corrosion-induced surface degradation in ship hulls necessitates advanced protective solutions. This study develops sustainable composite coatings by electrodepositing coconut shell particles (CSP) into Zn-CrO 3 matrices. This work introduces the novel use of coconut shell waste as a synergistic reinforcement to enhance both the anti-corrosion and mechanical properties of Zn-CrO 3 coatings. Coatings with increasing CSP content (0-6 g/L) were evaluated, demonstrating exceptional performance: Zn-20CrO 3 -6CSP achieved 93.325 Ω polarization resistance (297% higher than uncoated steel), reduced corrosion rate by 75% to 2.285 mm/year, and increased hardness by 90% to 259.3 Kgf/mm 2 . Microstructural analysis revealed a novel, transformative evolution from porous scale-like formations to compact knot-like structures that physically impede chloride penetration. These enhancements derive from the novel finding of CSP's dual functionality as both a pore-blocking barrier and grain-refining agent. The findings establish CSP as an effective eco-friendly reinforcement for marine coatings, offering superior corrosion protection and mechanical durability through sustainable waste valorization.